Computational Methods in Engineering

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In this paper , a fast method for automatic generation and scientific design of Persian letters is proposed. Scientific typeface design is an approach in which fonts are described by mathematical curves with well-defined parameters, where these parameters can be automatically tuned. METAFONT is a language suitable for the type of design used in this work. This language is particularly useful in designing Persian fonts because it can be used to simulate the pen movements of a calligrapher through automatic conversion of the scanned bitmap image of a font into a METAFONT program, which can in turn, produce the font at a high quality. A complete software has been implemented based on these algorithms that works interactively with the user to facilitate the font design.

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One of the great enemies of rubber compounds is heat. Heat will cause chemical and physical degradation of vulcanized rubber as well as a considerable loss in its strength. A major source of heat generation in a tire is due to internal friction resulting from the viscoelastic deformation of the tire as it rolls along the road. Another source of heat generation in a tire is due to its contact friction with the road. Prediction of the temperature rise at different parts of the tire will help to detect the behavior of the tire as regards its strength and its failure. In the present work, initially the data required for the thermal analysis of the tire are determined which include: the thermal conductivity of rubber compounds, the tire rolling resistance and its heat build-up rate. The thermomechanical analysis of a typical tire then follows based on the thermodynamics of an irriversible process. The mechanical dissipatives, i.e. the hystersis losses are assummed to be the major source of heat in the mathematical formulation. A finite element code is developed for two-dimensional heat transfer analysis of the tire. The results obtained show that the highest temperature rise will occur on the carcass-tread interface in a tire specially at heavy loading and under high speed conditions. Keywords: Heat Generation, Rubber, Contact Friction, Design, Finite Element, Viscoelastic Deformation

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In the process of the optimum design of aprons, solutions should be found for problems and such issues as the optimum area and dimensions of the apron, including the passenger and the cargo the number and dimensions of the gates on the basis of different types of aircraft parking configuration aircraft simulation and arrangement in different time periods of the given day at the airport. In this research, a mathematical model was developed for the analysis and design of airport aprons based on minimum transportation cost. Some of the parameters of transportation cost include user, capital, and operational costs. Moreover, based on the fundamentals of the mathematical model, a computerized simulation model was developed taking into consideration the actual parameters of design of airport aprons such as stochastic demand, passenger behaviour, and evaluation of analytical model. The results obtained from the computerized simulation model indicate that policies of the airport authorities and air carriers such as flight schedules, gate use strategy, the mix of aircraft fleet during the planning horizon, operational conditions, and economic cosiderations have significant impacts on the design of the aprons. Keywords: Airpornt, Apron, Optimization, Design.

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In the current engineering practices, buildings are commonly designed for an effective lifetime of 50 years. This lifetime can increase the cost of buildings with short lifetimes and can reduce the safety level of buildings with large lifetimes. In this paper, a “service-life factor” has been defined. Applying this factor into the nominal values of live, earthquake, wind, and snow loads, the effect of service-lifetime is taken into consideration. The study shows that the magnitude of seismic load can be reduced by 60% and those of other periodic loads by 30% for temporary buildings. An increase of 50% in the periodic loads was also observed for service-lifetime of 150– 200 years. These effects indicate a meaningful improvement in economy and safety of buildings if the service-life factor is considered

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Process optimization is one of the most important activities in todays competitive industries. the rather high cost of research and development has necessitated the development of experimental methods by which the factors affecting processes could be determined with minimum number of experiments. Over the last two decades, various types of experimental designs have been used. Among the different methods of experimental design such as complete and partial factorial and Latin squares design, the Taguchi method has found wide applications in some industrial divisions because of its comprehensive nature. In this paper, the laboratory scale flotation of the Sarcheshmeh copper ore which mainly consists of chalcocite was studied using the Taguchi method. The effects of seven factors namely collectors, Z11 (Xanthate) and R407 (Methyl isoboutyl carbonyl), frothers, pine oil and A65 (Polypropylene glycol), particle size, pH and flotation time were investigated. In addition to a significant reduction in cost and time of experimentation, the results indicated that a 5% increase in copper recovery could be obtained if all the factors are tested at their high experimental levels, as suggested by the Taguchi method. The optimal flotation time was also found to be 11 minutes.

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Contaminant transport analysis was performed for four selected solid waste landfill designs using the computer code POLLUTE. The diffusion coefficients were determined for the natural soils (aquitard) and compacted soils from the Urumia landfill site, using the diffusion tests. These coefficients along with the geometrical, physical, and chemical parameters of the natural soil and engineered layers, as well as the dominant boundary conditions were used in the analysis of the four selected designs for the landfill. These designs were evaluated for the contamination of the underlying aquifer in a specified period, using the drinking water standard for chloride ion. The comparisons showed that the fourth design which includes the engineered elements of a blanket type leachate collection layer and a compacted clayey liner underneath the landfill base, has more certainty in controlling the contaminant transport from the landfill base to the underlying aquifer. This type of landfill could be introduced as an optimum and semi-engineered design to be used for solid waste landfills in Iran.

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In this research, a new method called elastic surface algorithm is presented for inverse design of 2-D airfoil in a viscous flow regime. In this method as an iterative one, airfoil walls are considered as flexible curved beams. The difference between the target and the current pressure distribution causes the flexible beams to deflect at each shape modification step. In modification shape algorithm, the finite element equations of two-node Timoshenko beam are solved to calculate the deflection of the beams. In order to validate the proposed method, various airfoils in subsonic and transonic regimes are studied, which show the robustness of the method in the viscous flow regime with separation and normal shock. Also, three design examples are presented here, which show the capability of the proposed method.

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Weighted Simulation-based Design Method (WSDM) is recently developed as an efficient method for Reliability-
Based Design Optimization (RBDO). Despite simplicity, this method degrades effectiveness to obtain accurate optimum design for
high dimension RBDO. Besides, its application range is restricted to RBDOs including only random design variables. In the
present study, local search strategy is employed to enhance the accuracy of conventional WSDOM, and to reduce the computational cost. Besides, a shifting strategy is proposed to increase the application range of WSDM for handling general RBDO problems. The efficiency of the proposed methods is investigated by solving some structural reliability problems.
Comparisonof the obtained results with exact solutions confirms accuracy and superiority of the proposed method for
solving various engineering problems.

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In this paper, a robust optimization method is developed to solve the Satellite Launch Vehicle (SLV) trajectory design problem in the presence of uncertainties using a powerful Particle Swarm Optimization (PSO) algorithm. Given the uncertainties such as uncertainties in the actual values ​​of aerodynamic coefficients, engine thrust, and mass in the ascent phase of a SLV, it is important to achieve an optimal trajectory that is robust to these uncertainties; because it improves the flight performance, reduces the workload of the guidance-control system, and increases the reliability of the satellite. For this purpose, first the optimization problem is considered by using the criterion of minimizing the flight time of the SLV as a cost function, and three-dimensional equations of motion as constraints governing the problem. Then, by adding the mean parameters and the standard deviation of uncertainties in the cost function, a robust optimizer model is developed and the algorithm is used to numerically optimize the model. Monte Carlo's perspective has also been used to analyze the results of uncertainties and their continuous feedback to the optimization model. Finally, the optimal trajectory is obtained that is robust to the uncertainties. The resulting simulation results show the accuracy of this claim.